Chisel-edged, single-rooted, four in each jaw: the teeth used for biting into an apple
The incisors — two central and two lateral in each jaw
Anatomy · Head, neck & teeth
Incisor
The cutting teeth at the front of the mouth
Dentition · front teeth
The chisel-edged teeth at the front of each jaw, used for biting and cutting food. In the adult there are eight, two in each quadrant of the mouth (a central and a lateral incisor), and each has a single root. Children have eight milk incisors, and the permanent ones replace them between about six and nine years of age.
How to spot them
- ▸Thin, flat-edged crown ending in a straight cutting edge, with no cusps
- ▸A single root; the upper central pair are the widest of the front teeth
- ▸Four in each jaw: two central and two lateral
- ▸The lower central incisors are the smallest teeth in the mouth
What to know
The adult formula 2.1.2.3 begins with this tooth: two in each half-jaw
Incisors — the dental formula lists incisors, canines, premolars, molars per quadrant
Tooth 11 in the two-digit FDI system and tooth 8 in the American Universal system
The upper right central incisor
Notched, peg-shaped and narrowed towards the cutting edge, a sign of congenital syphilis named after a London surgeon
Hutchinson's incisors (Jonathan Hutchinson)
Scooped out on the back like a shovel, especially common in people of East Asian and Native American descent
Shovel-shaped incisors
Tusks of the elephant and the ever-growing front teeth of rodents are enlarged versions of these
Incisors, modified in elephants (tusks) and rodents (gnawing teeth)
Three small bumps called mamelons are found on the edge of the newly erupted tooth and are soon worn smooth
Mamelons on freshly erupted incisors
Key ideas
- Teeth are named by function: incisors cut, canines tear, premolars and molars grind.
- Dental formulae give teeth per half-jaw as incisors, canines, premolars, molars; humans have 2.1.2.3 in the permanent set and 2.1.0.2 in the milk set.
Quick-fire facts
- •Eight permanent incisors: two central and two lateral in each of the upper and lower jaws; eight milk incisors too
- •Adult dental formula: 2.1.2.3 per quadrant, 32 teeth in all. Milk formula: 2.1.0.2, 20 teeth in all
- •FDI two-digit notation: the first digit is the quadrant (1 upper right, 2 upper left, 3 lower left, 4 lower right; 5–8 for milk teeth), the second the tooth counted from the midline; the central incisor is number 1
- •Universal (US) numbering runs 1–32 from the upper right third molar; the incisors are numbers 7–10 (upper) and 23–26 (lower)
- •Milk teeth use letters A–T in the Universal system; the lower central incisors are the first to erupt, at about 6 months
- •The permanent lower central incisors erupt at about 6–7 years and the upper central at about 7–8 years
- •Latin incidere means 'to cut into'
- •The lower central incisors are the smallest teeth; the upper central incisors are the largest of the incisors
Drill it — 7 cards
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Sources
- OpenStax, Anatomy and Physiology 2e — 23.3 The Mouth, Pharynx, and Esophagus